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<H1>Module mod_include</H1>

This module is contained in the <code>mod_include.c</code> file, and
is compiled in by default. It provides for server-parsed html
documents. Several directives beyond the original NCSA definition have been
included in Apache 1.2 - these are flagged below with the phrase
"Apache 1.2 and above".  Of particular significance are the new flow 
control directives documented at the bottom.

<H2>Enabling Server-Side Includes</H2>

Any document with handler of "server-parsed" will be parsed by this
module, if the <CODE>Includes</CODE> option is set. If documents
containing server-side include directives are given the extension
.shtml, the following directives will make Apache parse them and
assign the resulting document the mime type of <CODE>text/html</CODE>:

<PRE>
AddType text/html .shtml
AddHandler server-parsed .shtml
</PRE>

The following directive must be given for the directories containing
the shtml files (typically in a <CODE>&lt;Directory&gt;</CODE> section,
but this directive is also valid .htaccess files if <CODE>AllowOverride
Options</CODE> is set):

<PRE>
Options +Includes
</PRE>

Alternatively the <A HREF="#xbithack"><CODE>XBitHack</CODE></A>
directive can be used to parse normal (<CODE>text/html</CODE>) files,
based on file permissions.  <P>

For backwards compatibility, documents with mime type
<code>text/x-server-parsed-html</code> or
<code>text/x-server-parsed-html3</code> will also be parsed
(and the resulting output given the mime type <code>text/html</code>).

<h2>Basic Elements</h2>

The document is parsed as an HTML document, with special commands embedded
as SGML comments. A command has the syntax:

<blockquote><code>
&lt;!--#</code><em>element attribute=value attribute=value ...</em>
<code> --&gt;
</code></blockquote>

The value will often be enclosed in double quotes; many commands only allow
a single attribute-value pair.  Note that the comment terminator
(<SAMP>--&gt;</SAMP>) should be preceded by whitespace to ensure that it
isn't considered part of an SSI token.
<p>
The allowed elements are:<p>

<dl>

<dt><strong>config</strong>
<dd>
This command controls various aspects of the parsing. The valid attributes
are:
<dl>
<dt>errmsg
<dd>The value is a message that is sent back to the client if an error occurs
whilst parsing the document.
<dt>sizefmt
<dd>The value sets the format to be used which displaying the size of a file.
Valid values are <code>bytes</code> for a count in bytes, or
<code>abbrev</code> for a count in Kb or Mb as appropriate.
<dt>timefmt
<dd>The value is a string to be used by the <code>strftime(3)</code> library
routine when printing dates.
</dl>

<dt><strong>echo</strong>
<dd>
This command prints one of the include variables, defined below.
If the variable is unset, it is printed as <code>(none)</code>.
Any dates printed are subject to the currently configured <code>timefmt</code>.
Attributes:
<dl>
<dt>var
<dd>The value is the name of the variable to print.
</dl>

<dt><strong>exec</strong>
<dd>
The exec command executes a given shell command or CGI script.
The IncludesNOEXEC <A HREF="core.html#options">Option</A> disables this command
completely. The valid attributes are:
<dl>
<dt>cgi
<dd>
The value specifies a (%-encoded) URL relative path to the CGI script.
If the path does not begin with a (/), then it is taken to be relative to
the current document. The document referenced by this path is invoked
as a CGI script, even if the server would not normally recognize it as
such. However, the directory containing the script must be enabled for
CGI scripts (with <A HREF="mod_alias.html#scriptalias">ScriptAlias</A>
or the ExecCGI <A HREF="core.html#options">Option</A>).<p>
The CGI script is given the PATH_INFO and query string (QUERY_STRING) of the
original request from the client; these cannot be specified in the URL path.
The include variables will be available to the script in addition to the
standard <A HREF="mod_cgi.html">CGI</A> environment.<p>
If the script returns a Location: header instead of output, then this
will be translated into an HTML anchor.<p>
The <code>include virtual</code> element should be used in preference to
<code>exec cgi</code>.
<dt>cmd
<dd>The server will execute the given string using <code>/bin/sh</code>.
The include variables are available to the command.
</dl>

<dt><strong>fsize</strong>
<dd>
This command prints the size of the specified file, subject to the
<code>sizefmt</code> format specification. Attributes:
<dl>
<dt>file
<dd>The value is a path relative to the directory containing the current
document being parsed.
<dt>virtual
<dd>The value is a (%-encoded) URL-path relative to the current document being
parsed. If it does not begin with a slash (/) then it is taken to be relative
to the current document.
</dl>

<dt><strong>flastmod</strong>
<dd>
This command prints the last modification date of the specified file,
subject to the <code>timefmt</code> format specification. The attributes are
the same as for the <code>fsize</code> command.

<dt><strong>include</strong>
<dd>
This command inserts the text of another document or file into the parsed
file. Any included file is subject to the usual access control. If the
directory containing the parsed file has the
<A HREF="core.html#options">Option</A>
IncludesNOEXEC set, and the including the document would cause a program
to be executed, then it will not be included; this prevents the execution of
CGI scripts. Otherwise CGI scripts are invoked as normal using the complete
URL given in the command, including any query string.
<!--%plaintext &lt;?INDEX CGI scripts, {\tt include} element and&gt; -->
<p>

An attribute defines the location of the document; the inclusion is done for
each attribute given to the include command. The valid attributes are:
<dl>
<dt>file
<dd>The value is a path relative to the directory containing the current
document being parsed. It cannot contain <code>../</code>, nor can it be an
absolute path. The <code>virtual</code> attribute should always be used
in preference to this one.
<dt>virtual
<dd>The value is a (%-encoded) URL relative to the current document being
parsed. The URL cannot contain a scheme or hostname, only a path and
an optional query string. If it does not begin with a slash (/) then it
is taken to be relative to the current document.
</dl>
A URL is constructed from the attribute, and the output the server
would return if the URL were accessed by the client is included in the parsed
output. Thus included files can be nested.

<dt><strong>printenv</strong>
<dd>This prints out a listing of all existing variables and their values.
    No attributes.
<dd>For example: <code>&lt;!--#printenv --&gt;</code>
<dd>Apache 1.2 and above.

<dt><strong>set</strong>
<dd>This sets the value of a variable.  Attributes:
<dl>
<dt>var
<dd>The name of the variable to set.
<dt>value
<dd>The value to give a variable.
</dl>
For example: 
  <CODE>&lt;!--#set var="category" value="help" --&gt;</CODE>
<dd>Apache 1.2 and above.

</dl>

<h2>Include Variables</h2>

In addition to the variables in the standard CGI environment, these are
available for the <code>echo</code> command, for <code>if</code> and
<code>elif</code>, and to any program invoked by the document.  

<dl>
<dt>DATE_GMT
<dd>The current date in Greenwich Mean Time.
<dt>DATE_LOCAL
<dd>The current date in the local time zone.
<dt>DOCUMENT_NAME
<dd>The filename (excluding directories) of the document requested by the
user.
<dt>DOCUMENT_URI
<dd>The (%-decoded) URL path of the document requested by the user. Note that
in the case of nested include files, this is <em>not</em> then URL for the
current document.
<dt>LAST_MODIFIED
<dd>The last modification date of the document requested by the user.
</dl>
<p>

<H2>Variable Substitution</H2>
<P> Variable substitution is done within quoted strings in most cases
    where they may reasonably occur as an argument to an SSI directive.
    This includes the
    <SAMP>config</SAMP>,
    <SAMP>exec</SAMP>,
    <SAMP>flastmod</SAMP>,
    <SAMP>fsize</SAMP>,
    <SAMP>include</SAMP>, and
    <SAMP>set</SAMP>
    directives, as well as the arguments to conditional operators.
    You can insert a literal dollar sign into the string using backslash
    quoting:

<PRE>
    &lt;!--#if expr="$a = \$test" --&gt;
</PRE>

<P> If a variable reference needs to be substituted in the middle of a
    character sequence that might otherwise be considered a valid
    identifier in its own right, it can be disambiguated by enclosing
    the reference in braces, <EM>&agrave; la</EM> shell substitution:

<PRE>
    &lt;!--#set var="Zed" value="${REMOTE_HOST}_${REQUEST_METHOD}" --&gt;
</PRE>

<P> This will result in the <SAMP>Zed</SAMP> variable being set to
    &quot;<SAMP>X_Y</SAMP>&quot; if <SAMP>REMOTE_HOST</SAMP> is
    &quot;<SAMP>X</SAMP>&quot; and <SAMP>REQUEST_METHOD</SAMP> is
    &quot;<SAMP>Y</SAMP>&quot;.

<P> EXAMPLE: the below example will print "in foo" if the DOCUMENT_URI is 
/foo/file.html, "in bar" if it is /bar/file.html and "in neither" 
otherwise:
<PRE>
    &lt;!--#if expr="\"$DOCUMENT_URI\" = \"/foo/file.html\"" --&gt;
    in foo
    &lt;!--#elif expr="\"$DOCUMENT_URI\" = \"/bar/file.html\"" --&gt;
    in bar
    &lt;!--#else --&gt;
    in neither
    &lt;!--#endif --&gt;
</PRE>

<H2>Flow Control Elements</H2>

These are available in Apache 1.2 and above.  The basic flow control
elements are:

<PRE>
    &lt;!--#if expr="<I>test_condition</I>" --&gt;
    &lt;!--#elif expr="<I>test_condition</I>" --&gt;
    &lt;!--#else --&gt;
    &lt;!--#endif --&gt;
</PRE>

<P> The <B><CODE>if</CODE></B> element works like an
    if statement in a programming language.  The test condition
    is evaluated and if the result is true, then the text until
    the next <B><CODE>elif</CODE></B>, <B><CODE>else</CODE></B>.
    or <B><CODE>endif</CODE></B> element is included in the
    output stream.

<P> The <B><CODE>elif</CODE></B> or <B><CODE>else</CODE></B>
    statements are be used the put text into the output stream
    if the original test_condition was false.  These elements
    are optional.

<P> The <B><CODE>endif</CODE></B> element ends the 
    <B><CODE>if</CODE></B> element and is required.

<P> <I>test_condition</I> is one of the following:

<DL>

<DT><I>string</I><DD>true if <I>string</I> is not empty

<DT><I>string1</I> = <I>string2</I><BR>
    <I>string1</I> != <I>string2</I>

<DD>Compare string1 with string 2.  If string2 has the form <I>/string/</I>
    than it is compared as a regular expression.
    Regular expressions have the same syntax as those found in the
    Unix egrep command.

<DT>( <I>test_condition</I> )
	<DD>true if <I>test_condition</I> is true 
<DT>! <I>test_condition</I>
	<DD>true if <I>test_condition</I> is false
<DT><I>test_condition1</I> && <I>test_condition2</I>
	<DD>true if both <I>test_condition1</I> and
	<I>test_condition2</I> are true 
<DT><I>test_condition1</I> || <I>test_condition2</I>
	<DD>true if either <I>test_condition1</I> or
	<I>test_condition2</I> is true 
</DL>

<P> "<I>=</I>" and "<I>!=</I>" bind more tightly than "<I>&&</I>" and
    "<I>||</I>". 
    "<I>!</I>" binds most tightly.  Thus, the following are equivalent:

<PRE>
    &lt;!--#if expr="$a = test1 && $b = test2" --&gt;
    &lt;!--#if expr="($a = test1) && ($b = test2)" --&gt;
</PRE>

<P> Anything that's not recognized as a variable or an operator is
    treated as a string.  Strings can also be quoted: <I>'string'</I>.
    Unquoted strings can't contain whitespace (blanks and tabs)
    because it is used to separate tokens such as variables.  If
    multiple strings are found in a row, they are concatenated using
    blanks.  So,

<PRE>
     <I>string1    string2</I>  results in <I>string1 string2</I>
    <I>'string1    string2'</I> results in <I>string1    string2</I>
</PRE>

<hr>
<h2>Directives</h2>
<ul>
<li><A HREF="#xbithack">XBitHack</A>
</ul>
<hr>


<h2><A name="xbithack">XBitHack</A></h2>
<!--%plaintext &lt;?INDEX {\tt XBitHack} directive&gt; -->
<strong>Syntax:</strong> XBitHack <em>status</em><br>
<strong>Default:</strong> <code>XBitHack off</code><br>
<Strong>Context:</strong> server config, virtual host, directory, .htaccess<br>
<Strong>Override:</strong> Options<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_include<p>

The XBitHack directives controls the parsing of ordinary html documents.
This directive only affects files associated with the MIME type
<CODE>text/html</CODE>. 
<em>Status</em> can have the following values:
<dl>
<dt>off
<dd>No special treatment of executable files.
<dt>on
<dd>Any file that has the user-execute bit set will be treated as a
server-parsed html document.
<dt>full
<dd>As for <code>on</code> but also test the group-execute bit. If it
is set, then set the Last-modified date of the returned file to be the
last modified time of the file. If it is not set, then no last-modified date
is sent. Setting this bit allows clients and proxies to cache the result of
the request.
<p><b>Note:</b> you would not want to use this, for example, when you
<code>#include</code> a CGI that produces different output on each hit
(or potentially depends on the hit).
</dl>
<p>

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